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Unjustifiable Extinctions

The world’s botanic gardens contain at least 30% of all known plant species, including 41% of all those classed as ‘threatened’, according to the most comprehensive analysis to date of diversity in ‘ex situ’ collections: those plants conserved outside natural habitats.

The study, in September 2017 in the journal Nature Plants, found that the global network of botanic gardens conserves living plants representing almost two-thirds of plant genera and over 90% of plant families. However, researchers from the University of Cambridge discovered a significant imbalance between temperate and tropical regions. The vast majority of all plants species grown ex situ are held in the northern hemisphere. Consequently, some 60% of temperate plant species were represented in botanic gardens but only 25% of tropical species, despite the fact that the majority of plant species are tropical.

For the study, researchers analysed datasets compiled by the Botanic Gardens Conservation International (BGCI)….

“The global network of botanic gardens is our best hope for saving some of the world’s most endangered plants,” said senior author Dr Samuel Brockington, a researcher at Cambridge’s Department of Plant Sciences as well as a curator at the University’s own Botanic Garden.
“Currently, an estimated one fifth of plant diversity is under threat, yet there is no technical reason why any plant species should become extinct. “If we do not conserve our plant diversity, humanity will struggle to solve the global challenges of food and fuel security, environmental degradation, and climate change.”

The plants not currently grown in botanic gardens are often more interesting than those that are, say the researchers. Hydrostachys polymorpha, for example, an African aquatic plant that only grows in fast flowing streams and waterfalls, or the tiny parasitic plant Pilostyles thurberi – only a few millimetres long, it lives completely within the stem tissue of desert shrubs. Species from the most ancient plant lineages, termed ‘non-vascular’ plants, are currently almost undocumented in botanic gardens – with as few as 5% of all species stored in the global network. These include plants such as the liverworts and mosses.

“Non-vascular species are the living representatives of the first plants to colonise the land,” said Brockington. “Within these plants are captured key moments in the early evolutionary history of life on Earth, and they are essential for understanding the evolution of plants”